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FHWA Highway Safety Programs

A Guide to Developing Quality Crash Modification Factors


This guide provides direction to agencies interested in developing crash modification factors (CMFs). It opens with a general discussion of CMFs, including definitions, purpose and application, and general issues related to CMFs. The document identifies several methodologies for developing CMFs, including an overview of each method, sample size considerations, strengths, and weaknesses. It also provides a process for selecting the most appropriate method.

Intended users include safety practitioners, consultants, and researchers. Users are expected to have experience and/or education in the theory and practice of road safety engineering, including basic analytical procedures and statistical concepts. It may be difficult to understand the implications of statistics and potential biases for those who do not possess a strong background in highway safety or statistics.

Tool Type:
Application Guide
Owner Source:
  • Federal Highway Administration (FHWA)

The guide is available free of charge at the following link: A Guide to Developing Quality CMFs.